To increase the performance of the engines, vehicles are equipped with such turbochargers as standard. The adjustable guide blades on the one hand can be put into a position in which the guide blade planes are approximately orientated tangentially to the turbine wheel, on the other hand a position can be adjusted in which the guide blade planes in axial view of the turbine wheel are approximately orientated radially to the turbine wheel axis. The first-mentioned position is adjusted if the exhaust gas flow of the engine is low. The other position is intended for an operating state with high exhaust gas flow. As a result, good efficiency of the turbine can be guaranteed in this manner independent of the intensity of the flow of the exhaust or propulsion gasses.
In terms of design, the guide blade arrangement, i.e. the variable turbine geometry (VTG) can be designed as a cartridge or cage or in another manner.
During turbocharger operation, very high temperatures are present in the radial gap, i.e. all elements or organs arranged adjoining the radial gap or in the radial gap are subjected to extraordinarily high thermal load. For this reason it must be expected that at or in the radial gap greater changes of the dimensions occur through thermal material expansions. In order to avoid distortions through dimensional changes on large assemblies joined as one piece it is practical to segment the walls forming the radial walls of the radial gap and to bring about the cohesion of the segments through resilient clamping. Thus dependent on the temperature each segment is able to change independent of adjoining segments. For this reason the design with a carrier ring clamped against stops by a thrust spring device mentioned at the outset is advantageous.
However, this design can still result in problems since the carrier ring with high thermal load can be deformed to a greater or lesser extent through the forces and counterforces of the thrust spring device and of the stops to which it is subjected. This results in that between the edges of the guide blades on the carrier ring side and the wall of the carrier ring located opposite these edges, gaps can form through which a larger gas flow passes, so that the control effect of the guide blades is reduced. As a result, the efficiency of the turbocharger can be significantly worsened. On the other hand, the opposite case can also occur, i.e. the guide blades can jam.